by Tim Hall on Tue Mar 15, 2011 8:21 pm
Aliyanna, I'll probably be able to better answer your question in a month after I get back from Sandor's miso/koji workshop. I seem to have trouble with koji too, despite several attempts. Hope to have it figured out soon.
On the one hand the rice is not supposed to be soft or rubbery, but on the other it seems it needs enough moisture to support fungal growth. I'm having a hard time knowing where that balance is. My koji does grow, but it doesn't seem to take off nearly as well as it should.
Re brown rice: Theoretically one could use all kinds of starchy substrates for koji. Wheat, barley, even sweet potatoes. But my understanding is it's sometimes difficult for the culture to grow on grains (like brown rice) that still have the bran intact. Apparently the bran can prevent the Aspergillus from growing into the grain and converting the endosperm.
If you want to make a semi-brown-rice amazake, you could probably make the koji from white rice, and there will be enough enzyme activity to convert a quantity of uncultured brown rice.